The present invention relates in general to a system for transferring articles and, more particularly, to a transfer system for moving an article between a conveyor used to transport the articles along a conveyor path and a work station.
In various fields, delicate or valuable articles must be safely transported between work stations and the like without damaging or destroying the articles. Articles requiring careful handling include, but are not limited to, pharmaceuticals, medical systems, flat panel displays, computer hardware such as disc drive systems, modems and the like, and semiconductor wafers. The articles are often transported from work station to work station by a conveyor. In many situations, the articles must be temporarily removed from the conveyor for processing. Preferably, the operation of the conveyor is not interrupted while the article is removed from the conveyor. After the processing has been completed, the articles must then be carefully returned to the conveyor for transport to the next work station.
With many applications, the value of the articles increases after the articles are processed at each work station. For example, integrated circuits are manufactured by forming a plurality of layers on a substrate such as a semiconductor wafer. The work stations used to form integrated circuits include machines for depositing the individual layers as well as machines for cleaning and/or conditioning the substrate at various stages. With advances in technology, integrated circuits have become increasingly complex and typically include multiple layers of intricate wiring. The size of the integrated circuits has decreased, greatly increasing the number of such devices on a single wafer. As a result of the increased complexity and decreased size of the integrated circuits, the value of the semiconductor wafer increases substantially as the wafer progresses through the various processing stages. The standard size of the semiconductor wafers will increase from 200 mm to 300 mm or larger in the next few years, further increasing the number of integrated circuits which may be formed on a single wafer and therefore the value of each wafer. For articles such as semiconductor wafers, considerable care must be taken when handling the articles to reduce the risk of damaging the articles and incurring significant monetary losses.
Some articles, such as semiconductor wafers, must be retained in a clean room environment during processing to preserve the purity of the layers deposited on the wafer. The requirement of a clean room environment places additional constraints on the handling of these articles. For additional protection against contaminants, the semiconductor wafers are typically retained in sealed transport devices, such as pods as they are moved throughout the manufacturing facility to minimize any exposure to the environment outside of the processing machines. The pods are used to transport the articles along the conveyor.
The input station of the semiconductor processing machines often include a load port for the automatic removal of one or more wafers from the transport pod in a protected environment. The load port shelf may be moved a limited distance, on the order of a couple of inches, to move the pod toward and away from a load port seal at the machine entrance. This horizontal shifting of the pod is minimal and does not serve any function in the movement of the pod to the load port or the transfer of the pod between the conveyor and load port.
A system for safely and accurately moving a transport pod or other article between a conveyor and a work station is desirable. An article transfer system which may be used to move the articles without significantly disrupting the continued operation of the conveyor is also desirable. Similarly, a transfer system which may be used to support the article at the work station is desirable.
It is a primary object of the present invention to provide a system for transferring articles between a conveyor and a work station.
It is a further object of the present invention to provide a system for moving articles between a conveyor and a work station in a clean room environment.
It is another object of the present invention to provide a transfer system which may be used to automatically transfer articles between the conveyor and work station without significantly interrupting operation of the conveyor.
It is yet another object of the present invention to provide a transfer system for moving a transport pod or other container retaining one or more semiconductor wafers between a conveyor and the load port of a processing machine.
A more general object of the present invention is to provide a transfer system which may be efficiently constructed, operated and maintained.
Another object of the present invention is to provide a transfer system which is compatible with a motion axis that is already included in standard load ports.
In summary, the present invention provides a transfer system for moving an article between a conveyor and a workstation. The transfer system generally includes an elevator system and a support assembly positioned adjacent to the work station. In the illustrated application, where the work station is a semiconductor processing machine, the support assembly is preferably mounted to the machine. The elevator system includes a lift device is configured to engage the article being transported along the conveyor and raise the article above the conveyor. The lift device is movable between a stand-by position in which the lift device positioned so that articles transported by the conveyor may move past the lift device, and an actuated position with the lift device holding the article above the conveyor. The support assembly includes a shelf member or equivalent support means for retaining the article at the workstation and a displacement mechanism for moving the shelf member or equivalent support means between the conveyor and the lift device to carry the article between the conveyor and the work station.
The present invention also provides a method of moving articles between a work station and conveyor. The method includes the steps of moving a support to engage the article and lift the article from a first position to a second position above the conveyor and extending a shelf of a load port to the conveyor and inserting the shelf between the article and the conveyor. After the step of extending a shelf, the support is moved to deposit the article onto the shelf, and after the step of moving the support, the shelf is retracted to the load port.
Additional objects and features of the invention will be more readily apparent from the following detailed description and appended claims when taken in conjunction with the drawings.